The potential uses and recognized advantages of employing electrical energy for surgical purposes are ever-increasing. In particular, for example, electrosurgical techniques are now being widely employed to provide highly-localized tissue cutting and coagulation capabilities in both open and laparoscopic applications, thereby yielding reduced tissue trauma and additional advantages relative to prior traditional surgical approaches.
Electrosurgical techniques entail the use of a hand-held instrument or pencil having one or more working surfaces that transfer radio frequency (RF) electrical energy to the tissue (e.g. via a stainless steel scalpel or blade), a source of radio frequency (RF) electrical energy (e.g. a dedicated electrosurgical generator), and a return path device, commonly in the form of a return electrode pad positioned under a patient or a smaller return electrode positionable in bodily contact at or immediately adjacent the surgical site. The return path device provides a return electrical path from the patient tissue to the energy source. More particularly, both the instrument and the return path device are interconnected via electrically conductive wire(s) to the source of the radio frequency electrical energy which serves as both the source and the sink for the electrical energy to produce a complete electrical circuit. When a hand-held instrument and return path pad are utilized, the electrosurgical technique is termed monopolar. When a hand-held instrument and smaller return path electrode (i.e. selectively positionable at or immediately adjacent the surgical site) are utilized the electrosurgical technique is termed bipolar.
The waveforms produced by the radio frequency electrical source may be designed to yield a predetermined electrosurgical effect, namely tissue cutting or coagulation. In this regard, prior to the present invention, tissue cutting/coagulation effects have been the sole parameters considered in the design of electrostirgical waveforms.
Despite the advantages associated with known electrosurgical techniques, one attendant implication has been that deposits build up on the surgical instrument working surfaces that convey electrical energy to the tissue. The deposits form from matter that is ejected from the tissue and contacts the working surfaces, and from tissue matter that directly contacts the working surfaces and stick thereto. The working surfaces typically heat up as the electrical energy is applied to them, which in turn causes the deposited materials to change their physical and chemical composition. The deposits are commonly referred to as eschar. As eschar builds up and becomes increasingly thick, it progressively detracts from the corresponding electrosurgical procedure (e.g. cutting). That is, for example, the eschar builds to such a thickness that a surgeon must interrupt the surgical procedure to clean the instrument's working surfaces. Cleaning commonly entails the use of abrasive pads that scrape the encrusted eschar from the working surfaces of the instrument. As the surgical procedure continues, the described cleaning procedure must be completed with increasing frequency. Such stoppages for cleaning interfere with the efficacy of the surgical procedure, cause delays and otherwise result in significant annoyance to medical practitioners.
In addition to the use of abrasive pads, other approaches to deal with eschar deposits have been restricted to treating electrosurgical blades with or making blades from materials intended to reduce eschar build-up. Such methods have included electropolishing stainless steel electrosurgical blades. Other methods have included covering the working surfaces with fluorinated hydrocarbon materials (see, e.g., U.S. Pat. No. 4,785,807), and coating niobium blades with a niobium oxide (see, e.g., U.S. Pat. No. 5,030,218). These approaches for eschar reduction still result in eschar deposits and require a focused effort on the part of medical practitioners to remove the eschar deposit from the working surfaces of the surgical instrument. Additionally, such cleaning frequently removes or otherwise degrades the special surface treatments of the working surfaces, which reduces their efficacy as the surgical procedure progresses.